reserve B,C,D for Category;

theorem
  for S being Contravariant_Functor of C opp,B, c being Object of C opp
  holds (Obj /*S).(opp c) = (Obj S).c
proof
  let S be Contravariant_Functor of C opp,B, c be Object of C opp;
  thus (Obj /*S).(opp c) = (Obj S).((opp c) opp) by Th34
    .= (Obj S).c;
end;
